Extrasolar Planets

Meta-modelling The Climate Of Dry Tide Locked Rocky Planets

By Keith Cowing
March 28, 2022
Filed under
Meta-modelling The Climate Of Dry Tide Locked Rocky Planets
Two-day averaged potential temperature field in Earth-like case of Table 2 with ps “ 1 bar and F‹ “ 1366 W m´2 . Plotted values belong to the interval r248 K, 376 Ks. Outside of this interval, the color is set to that of the closest bound. The 2-D instance of the meta-model (32 ˆ 50 grid) is used. The latitudes 900 and ´900 correspond to the sub- and anti-stellar points, respectively.

Rocky planets hosted by close-in extrasolar systems are likely to be tidally locked in 1:1 spin-orbit resonance, a configuration where they exhibit permanent dayside and nightside.

Because of the resulting day-night temperature gradient, the climate and large-scale circulation of these planets are strongly determined by their atmospheric stability against collapse, which designates the runaway condensation of greenhouse gases. To better constrain the surface conditions of rocky planets located in the habitable zone of their host star, it is therefore crucial to elucidate the mechanisms that govern the day-night heat redistribution.

As a first attempt to bridge the gap between multiple modelling approaches ranging from idealised models to 3-D General Circulation Models (GCM), we developed a General Circulation Meta-Model (GCMM) able to reproduce both the closed-form solutions provided by analytical models and the numerical solutions obtained from GCM simulations. We used this approach to characterise the atmospheric stability of Earth-sized rocky planets with dry atmospheres containing CO2, and we benchmarked it against 3-D GCM simulations using THOR GCM. We observe that the collapse pressure below which collapse occurs can vary by ~40% around the value predicted by analytical scaling laws depending on the mechanisms taken into account among radiative transfer, atmospheric dynamics, and turbulent diffusion.

Particularly, we find (i) that the turbulent diffusion taking place in the dayside planetary boundary layer (PBL) globally tends to warm up the nightside surface hemisphere except in the transition zone between optically thin and optically thick regimes, (ii) that the PBL also significantly affects the day-night advection timescale, and (iii) that the slow rotator approximation holds from the moment that the normalised equatorial Rossby deformation radius is greater than 2.

Pierre Auclair-Desrotour, Russell Deitrick, Kevin Heng
Comments: 32 pages, 16 figures, accepted for publication in Astronomy & Astrophysics
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
MSC classes: 85-02
Cite as: arXiv:2203.14929 [astro-ph.EP] (or arXiv:2203.14929v1 [astro-ph.EP] for this version)
Submission history
From: Pierre Auclair-Desrotour
[v1] Mon, 28 Mar 2022 17:30:40 UTC (2,958 KB)

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